Uwe : How to create real time plot with auto scale axis and zooming functionality.

[vinothrajendran]

I have a scenario where i should be plotting real time data for an hour. But first i have to display only first 2 min in x axis, when time reaches 2 min i should expand my scale to 4 min and it should keep on going......

I tried using QwtPlotDirectPainter which is efficient but after 2 min , i dont know how to rescale it to 4 min ....

But if i use QwtPlotCurve with replot() and autoaxisscale() feature , i am able to acheive this, but with delay in plotting as time increases ....

Any help will be appreciated.....


I feel QwtPlotDirectPainter will be efficient, please give a solution with it.....
I tried looking at Oscilloscope example , i could not get it....If possible try give source code with explanation......

[Uwe]

I have a scenario where i should be plotting real time data for an hour. But first i have to display only first 2 min in x axis, when time reaches 2 min i should expand my scale to 4 min and it should keep on going......

void YourPlot::addPoint( const QPointF &pos )
{
    const QwtInterval interval = axisInterval( QwtPlot::xBottom );
    if ( pos.x() > interval.maxValue() )
    {
        setAxisScale( interval.minValue(), interval.maxValue() + ... );
        replot();
    }
 
    ...
}

void YourPlot::addPoint( const QPointF &pos )
{
    const QwtInterval interval = axisInterval( QwtPlot::xBottom );
    if ( pos.x() > interval.maxValue() )
    {
        setAxisScale( interval.minValue(), interval.maxValue() + ... );
        replot();
    }

    ...
}

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